Jackass much? Indeed, that link does answer the
question. I figured someone in the world would
have thought of the idea and acted upon it.
Thanks. (Incidentally, the link provided is not in
the first one hundred results for that search
string. Odd!)

{The CSS or html on this site is a bit wonky.}
Anyway, to 21_Quest: for instance: take leftovers
to work. The least filthy place to store a fork
during the day is with the food--and during the
microwave moments--in the oven itself. Most
disposable utensils are flimsy or brittle. I do not
know how hot a non-brittle, non-flimsy material
would get. Good point!

It's yet another microwave oven myth that you can't safely microwave metal cutlery and other objects. Under some conditions, metal can create conditions that are, depending on the observer, entertaining or alarming, possibly somewhat damaging to the oven, or in extreme cases, actually dangerous (but only if left running unattended for a long time, in which case there may be a risk of containment failure or fire).

Those conditions are:
1) Food entirely enclosed in thick metal. This creates a condition equivalent to running the oven completely empty, and is probably bad for the magnetron, but not massively dangerous.

2) Very thin metal, such as steel wool or thin strips of foil. These can heat up and melt, and often create sparks.

3) Metal that is in point contact with, or separated by a very short distance from, another piece of metal (including the metal case of the oven). This creates sparks.

If there is a reasonable amount of food in there as well, 2) and 3) are fairly mild, although the finish on the oven could be damaged, and the metal objects could become hot and burn you if you picked them up.

Ordinary metal cutlery is perfectly safe, as long as it doesn't brush against the side of the oven or another piece of metal. For instance, a spoon in a mug of coffee, or a fork on a plate of food, is a complete non-event.

Wood, on the other hand, can heat up and even char or burst into flames (but only in extreme cases, such as a smallish piece of wood, on its own, heated for a longish time).

I should add that the tines of a fork do heat up (but not alarmingly) if exposed, as they are on the thinnish side. Shoving the fork into some food prevents that.

Forks should not be microwaved, as at minimum it
can easily damage the fork. If the arc from the tines
brushes the metal edge of the microwave it can also
damage that. Spoons or non-serated knives are
much less of a risk. Likewise thin metal decorations
on dishes can be significantly damaged, and damage
the surrounding ceramic and glaze.

[MechE] I think I made all those points, except that I consider //Forks should not be microwaved, as at minimum it can easily damage the fork// to be far too strong - unless the fork is on its own. I just microwaved an ordinary dining fork, completely exposed alongside a container with about 250 mL of water. After 2½ minutes, the water was nearly boiling, but the fork was just barely warm. Try it!

Note that all my statements above are based on my own understanding and experimenting, and not on the common microwave do and don't lists, which are on the cautious side.

I have deliberately melted and vaporised thin metal (and melted glass and stone), generated arcs and plasmas, charred and burned wood, and more. I have also tried and confirmed all the things that I claim to be non-events.

I can easily believe that; but the piece of stainless steel would have to be (a) very thin or pointy, or (b) moderately thin or pointy and the only thing in the oven.

Just for fun, I gave a fork 10 seconds on high with nothing else in the oven. Sure enough, it gave a bright discharge flash from one of the tines; if I'd left it there much longer, I would expect to get visible damage.

A good rule of thumb is that "the power has to go somewhere". A plate of food or a cup of water is a much stronger microwave absorber than a fork, and a bigger target; but when there's nothing else to absorb the microwaves, the fork (potentially) cops it all.